1. Field of the Invention
The present invention relates to an image reading apparatus in a system that certifies the originality of a paper sheet by using a paper fingerprint that represents the bumps and entanglements of random fibers on the paper surface, as well as a control method of the image reading apparatus and an image reading method.
2. Description of the Related Art
Because the bumps and entanglements of fibers on the surface of a paper sheet cannot be controlled in the manufacturing process, each individual paper sheet has a different pattern, similarly to the way in which the fingerprint of each person is unique. This unique pattern is referred to as a “paper fingerprint”. By identifying and managing paper fingerprint information that represents this kind of paper fingerprint, the paper fingerprint can be utilized as original certifying means.
However, when it is attempted to acquire the aforementioned paper fingerprint information using a general-purpose scanner, there is a problem that the amount of light of the scanner light source at the time of normal scanning is too large, and is it not possible to extract the paper fingerprint information because the image of the location (background of the paper sheet) from which it is desired to acquire the paper fingerprint information is scanned as white.